In the fields of advertising and retail, knowledge about a consumer, e.g., the consumer's affinities, likes, dislikes, opinions, hobbies, interests, etc., tends to be useful. For example, knowing a consumer's likes may be used to better recommend a product to that consumer.
Such knowledge about a consumer may be acquired directly from that consumer. However, it is often the case that consumers have reservations about providing such information and defer or avoid doing so.
Separate from the above mentioned fields, methods of extracting topics discussed in a text document, and assessing the author's sentiment with respect to the text document's topics, are known.